Spectrophotometric results

Objective Evaluation of Color. In recent years a method has been devised and internationally adopted (International Commission on Illumination, I.C.I.) that makes possible objective specification of color in terms of equivalent stimuli. It provides a common language for description of the color of an object illuminated by a standard illuminant and viewed by a standard observer (H). Reflectance spectro-photometric curves, such as those described above, provide the necessary data. The results are expressed in one of two systems the tristimulus system in which the equivalent stimulus is a mixture of three standard primaries, or the heterogeneous-homogeneous system in which the equivalent stimulus is a mixture of light from a standard heterogeneous illuminant and a pure spectrum color (dominant wave-length-purity system). These systems provide a means of expressing the objective time-constant spectrophotometric results in numerical form, more suitable for tabulation and correlation studies. In the application to food work, the necessary experimental data have been obtained with spectrophotometers or certain photoelectric colorimeters. 

Klooster, N. Th. M., van der Trouw, F. Mandel, M. (1984). Solvent effects in polyelectrolyte solutions. 3. Spectrophotometric results with (partially) neutralised poly(acrylic acid) in methanol and general conclusions regarding these systems. Macromolecules, 17, 2087-93. 

This paper has examined the role of calibration and evaluation of measurement uncertainty in clinical laboratories arising from the request for traceability assurance. To produce results which are accurate and reliable within the stated uncertainty, all uncertainties of the quality measurement process and the traceability chain should be demonstrated. Also, the quality of a spectrophotometric result depends critically on RMs and photometric systems whose traceability have been properly demonstrated. 

TRI/CAL] Tribalat, S., Caldero, J. M., Use of simple kinetics in the study of thiocyanate complexes and chlorides. Comparison of some spectrophotometric results, Compt. Rend., 255, (1962), 925-927. Cited on pages 146, 147, 232,233, 304. 

NB A model compound restricted to die essential features of the 3-hydroxypyridine portion (giving die second set of pKg, values) was used to simplify the data analysis. A third pJCa value, corresponding to the dimediylamino group, has not been reported. The microconstants for the 3-hydroxypyridine system were reported from a combination of potentiometric and spectrophotometric results. 

Based on the NMR and UV-Vis spectrophotometric results, the following models can be proposed for the four systems investigated (Fig. 8). Both Co(II) and Ni(II) atoms are retained at the interface in the different systems. More than one hexanol molecule enters the first coordination shell of Ni(II) ions. Co(II) interacts with one hexanol molecule in the CTAB-hexanol-water microemulsions, whereas both decanol and Triton X-100 molecules enter its first coordination shell. The Fe(III) ions are strongly hydrated in the inner water cores, and no hexanol molecules are able to replace the strongly held water molecules with this highly charged ion. Finally, the CTA ions interact indirectly only with the positively charged complexes. 

Hydration of tiglyl CoA by these tissue preparations was readily demonstrated spectrophotometrically, resulting from the disappearance of the ultraviolet absorption band of the double bond. The enzyme responsible for the hydration is probably enoyl hydrase (crotonase). 

As a Chatt-Ahrland type A or Pearson hard cation, association of Am with inorganic ligands proceeds initially through electrostatic interactions to form outer-sphere complexes. However, in some cases (e.g. F", SO "), there is evidence that the ligand displaces the water of hydration, at least to some extent, to form inner-sphere complexes. Spectrophotometric results of Marcus and Shiloh [124] also provide evidence for inner-sphere complexation of chloride and nitrate ions to Am in concentrated LiCl and UNO3 solutions, respectively. Preparation of the solid compound [(CeHslsPHjsAmQg, containing the octahedral hexahalide complex AmCl, has been described by Ryan [107]. 

Isomerization of [Co(en)(NH3)3(OH)] + and of [Co(en)(NH3)2(OH)2]+ has been extensively studied by spectrophotometry in dilute aqueous solution. Recent kinetic results for the former isomerization obtained by the use of Co n.m.r. spectroscopy, in concentrated solutions, are consistent with the early spectrophotometric results. The [Co(en)(NH3)2(OH)2]+ cation exists in three isomeric forms. The observed isomerization paths and their respective rate constants, also obtained by Co n.m.r. spectroscopy, are shown in Table 27. The proposed mechanism for these isomerizations involves reversible dissociation of one end of the ethylenediamine ligand from the cobalt. Isomerization of mer- or yhc-[Co(en)(NH3)3(OH)] + was not detected, even after... 

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